Synthesis and photophysics of organometallics containing ligand-centered and charge-transfer excited states.

摘要

The present thesis describes the synthesis and photophysics of a variety of organometallic Pt(II) and Re(I) diimine complexes containing ligand-centered and charge-transfer excited states. The photophysical properties have been investigated by electronic spectroscopy, steady-state and time-resolved photoluminescence (TRPL) at room temperature and 77 K, laser flash photolysis, and cyclic voltammetry measurements. In terms of the newly designed synthetically facile Pt(II) diimine bis(arylacetylide) complexes, either charge transfer emission or room temperature phosphorescence in fluid solution has been observed. In one particular instance, the excited state properties can be best described as possessing a combination of metal-to-ligand charge transfer (MLCT) and intraligand (IL) character, where the low-lying state dominates the behavior and solvent media allows transitioning between these two limits.; The synthesis and photophysical properties of two new Re(I) complexes are also reported: fac-Re(phen-C≡CH)(CO)3Cl, phen-C≡CH is 5-ethynyl-1,10-phenanthroline, along with its Au(I)-acetylide analog fac-Re(phen-C≡C-AuPPh3)(CO) 3Cl. In these two phen-C≡C-R containing molecules, the room temperature excited state decay is consistent with a MLCT assignment whereas at 77 K, the lowest excited state is clearly 3IL, localized within the respective diimine ligand. The PL and time-resolved absorption data in fac-Re(phen-C≡C-AuPPh3)(CO)3Cl indicate that in the charge-transfer excited state, the electron is delocalized into the Au-acetylide fragment which aids in extending the lifetime of the excited state.